158 CARBONIFEROUS PERIOD. 



Suborder PODOPeTHALMA. 



Fajiilt EUOMPHALID^. 



Genus EUOMPHALUS Sowerby, 1815. 



Euomphalus pernodosus Meek and Worthen. 

 Plate XII, fig. 2 a aud h. 



Straparollus {Euomphalus) pernodosus Meek und Worthen, 1870, Proc. Acad. Nat. Sci. 



Phila., 45. 

 Straparollus (Eiiomplialus) pernodosus Meek and Worthen, 1873, Geol. Surv. Illinois, 



V, G04. 



Shell rather above medium size when full grown, nearly discoidal, the 

 spire being only very slightly elevated, and the inner portion of it being 

 quite flat, or even slightly depi'essed ; test thick ; volutions five or six, the 

 upper side flattened and sloping gently inward to the distinct sutm-e, outer 

 side flattened convex, under side rounding and sloping into the umbilicus ; 

 the angle formed by the upper and outer sides constituting- a distinct carina, 

 which is rugose or corriigated upon the outer volution ; upon the under 

 side of the volutions there is a row of moderately large, rounded nodes, 

 separated by spaces of about their own width, those of the last half of 

 tlie outer volution, and apparently those also of the two or three inner 

 volutions, being obsolete ; umbilicus moderately broad and deep, showing 

 all the inner volutions. 



Surface marked by strise, distinct lines, and even ridges, of growth. 

 None of the specimens in the collections are quite perfect, but their identity 

 with JE. pernodosus is unmistakable. The largest example measures about 

 four aud a half centimeters in diameter of coil. The types of the species 

 measured one centimeter more. This well-marked species is comparatively 

 rare, and, so far as I know, it has been found only at the locality which 

 furnished the type-specimens and that from which those in tlie collections 

 were obtained. The former were from the Lower Coal-Measures of Illinois. 



It is quite distinct from every other species known to me, and may be 

 easily recognized by its cai'ina upon the outer side of the volutions above 

 and its strong nodes below. 



Position and locality. — Sti'ata of the Carboniferous period ; at the Mesa, 

 Carrizo Eiver, Arizona. 



